EMERGENCE OF CARBAPENEM RESISTANCE AMONG EXTENDED SPECTRUM BETA-LACTAMASE ISOLATE OF Escherichia coli FROM CLINICAL SPECIMENS IN A TERTIARY HOSPITAL, NIGERIA

Abstract

Extended-spectrum beta -lactamases (ES beta Ls) are a rapidly evolving group of beta -lactamases which share the ability to hydrolyze third-generation cephalosporins and aztreonam yet are inhibited by clavulanic acid. In this study, the aim was to determine the susceptibility of ES beta L producing clinical isolates of Escherichia coli across various antimicrobial agents according to the Clinical Laboratory Standard Institute (CLSI) new breakpoints. Sixty five clinical isolates of Escherichia coli were collected from a Tertiary Hospital in Nigeria of which forty six ES beta L-producing isolates emerged. Presence of ES beta L was determined by double-disk synergy test, DNA extraction and amplification of ES beta L genes - blaSHV, blaTEM, blaCTX-M by Polymerase Chain Reaction. Susceptibility of the ES beta L-producing isolates was determined by the CLSI agar diffusion method. Utilizing the CLSI new breakpoints, 76.09%, 73.91%, 73.91% and 63.04% were resistant to Cefotaxime, Ceftazidime, Aztreonam and Cefepime respectively. While, 19.6%, 15.2%, 21.7% and 40% were susceptible to Cefotaxime, Ceftazidime, Aztreonam and Cefepime respectively. Furthermore, though a significant number of ES beta L-producing isolates were susceptible to carbapenem; ES beta L isolates that harboured the blaSHV, blaTEM, blaCTX-M genes showed resistance to carbapenem. Thus, carbapenem-resistant ES beta L-producing isolates emerged from this study. In conclusion, Nigeria is a developing country affected by the spread of bacterial strains harbouring ES beta L and with the emergence of carbapenem resistance; it is certain to create significant therapeutic problems as carbapenem is the drug of choice for serious infections caused by ES beta L-producing Escherichia coli.